404 brake saga
  • Register
  • Help
Page 1 of 3 123 Last
Results 1 to 25 of 57
Like Tree1Likes

Thread: 404 brake saga

  1. #1
    Member
    Join Date
    May 2015
    Location
    Adelaide
    Posts
    102

    Default 404 brake saga

    Hi all,

    I jumped in the lad's 404 the other day to go to the shops. (Think driveway scene from The Castle) and I am very glad I did. The brakes were awful. HUGE amount of pedal travel, and very soft. He, of course, didn't think to mention this.

    SO, back to the garage and out with the tools and pull it all apart.

    First of all, the car is a late 68 or early 69, with factory disc brakes and standard (non thermo stable) drums on the back. (At least, I assume this is the case, they look very "normal" and simple to me.)

    The master cylinder condition was pretty good, it has been rebuilt in the last ten years and still has the hone marks. The seals were all in good condition, but I will replace them as a matter of course.

    Then there's the booster. The existing booster looks very much like it was a VH44. I recently bought a remanufactured VH40 from a guy here in South Australia whom I trust, so I figured I would swap the two, which I did. I have mounted it using the brackets that came with it, in the fore-and-aft orientation that I've seen documented here on AussieFrogs.

    I assembled everything, bled the whole lot, and took it for a drive.

    Not good.

    Pedal travel is still very bad, but this time I could pump the brakes up and get a very good pedal feel if I tried. However the extra boost made the brakes super-sensitive and I locked the back up a couple of times without meaning to. Then, on the way back from the very test drive, the brakes started to jamb on somewhere, in a very unpredictable way.

    So, what do I do next?

    Oh, and also for the record, I have checked the rear drums and the pads are adjusted pretty well.
    There is no loss of fluid apparent, and there was no loss apparent prior to the work being done.

    Help please!

    Advertisement


    And as a separate aside, we were both very happy with the level of boost from the VH44. Certainly it was heavy, but no unpleasant, so all else being equal, I'd be happy to buy a new VH44 and fit it, unless there was a reason not to.

    Matt

  2. #2
    1000+ Posts robmac's Avatar
    Join Date
    Nov 2004
    Location
    Melbourne / Caulfield
    Posts
    18,772

    Default

    Quote Originally Posted by Gilow View Post
    Hi all,

    I jumped in the lad's 404 the other day to go to the shops. (Think driveway scene from The Castle) and I am very glad I did. The brakes were awful. HUGE amount of pedal travel, and very soft. He, of course, didn't think to mention this.

    SO, back to the garage and out with the tools and pull it all apart.

    First of all, the car is a late 68 or early 69, with factory disc brakes and standard (non thermo stable) drums on the back. (At least, I assume this is the case, they look very "normal" and simple to me.)

    The master cylinder condition was pretty good, it has been rebuilt in the last ten years and still has the hone marks. The seals were all in good condition, but I will replace them as a matter of course.

    Then there's the booster. The existing booster looks very much like it was a VH44. I recently bought a remanufactured VH40 from a guy here in South Australia whom I trust, so I figured I would swap the two, which I did. I have mounted it using the brackets that came with it, in the fore-and-aft orientation that I've seen documented here on AussieFrogs.

    I assembled everything, bled the whole lot, and took it for a drive.

    Not good.

    Pedal travel is still very bad, but this time I could pump the brakes up and get a very good pedal feel if I tried. However the extra boost made the brakes super-sensitive and I locked the back up a couple of times without meaning to. Then, on the way back from the very test drive, the brakes started to jamb on somewhere, in a very unpredictable way.

    So, what do I do next?

    Oh, and also for the record, I have checked the rear drums and the pads are adjusted pretty well.
    There is no loss of fluid apparent, and there was no loss apparent prior to the work being done.

    Help please!

    And as a separate aside, we were both very happy with the level of boost from the VH44. Certainly it was heavy, but no unpleasant, so all else being equal, I'd be happy to buy a new VH44 and fit it, unless there was a reason not to.

    Matt
    Check the anti lock valve on the diff is working.

    Check the flexible hoses for blocked internal bores. There are hoses on each front brake and a single hose on the torque tube.

    Always bleed the brakes with the rear wheels on the ground

    I'd also suspect master cylinder issues from hard experience and check the brake booster isn't leaking internally , ie check for gungy liquid inside the vacuum diaphragm area. Through the vacuum port.

  3. #3
    Member
    Join Date
    May 2015
    Location
    Adelaide
    Posts
    102

    Default

    Thank you Robmac,


    Quote Originally Posted by robmac View Post
    Check the anti lock valve on the diff is working.

    Any hints on how to do this?



    ....

  4. #4
    1000+ Posts robmac's Avatar
    Join Date
    Nov 2004
    Location
    Melbourne / Caulfield
    Posts
    18,772

    Default

    It's not easy -generally all you can do is check the piston moves when pressed. And of course the rear brakes don't lock up prematurely.

    I've not seen one leak.

    Here's a thought with car on it's wheels do you get any change in brake "feel" if you pull on the handbrake ?

    That would indicate the rear brakes are getting fluid to them.

    The only other way is to crack a brake fitting and look for fluid squirting.

  5. #5
    VIP Sponsor
    Join Date
    Aug 2000
    Posts
    9,137

    Default

    Better check which model it actually is. Does it have chrome tops to the door trims?

  6. #6
    1000+ Posts robmac's Avatar
    Join Date
    Nov 2004
    Location
    Melbourne / Caulfield
    Posts
    18,772

    Default

    I'd think with front disks and a booster It also has an anti lock valve.

  7. #7
    VIP Sponsor
    Join Date
    Aug 2000
    Posts
    9,137

    Default

    Could have had discs fitted to a 68, with important bits missing, or even wrong bits on a 1969. If a disc brake master is fitted to a 68 without adding the 1969 4 way junction on the cross member there won't be a line pressure valve for the rears and the pedal feel and level will be bad.Also, locking rears suggests no limiting valve on rear axle, or maybe just seized?

  8. #8
    Member
    Join Date
    May 2015
    Location
    Adelaide
    Posts
    102

    Default

    Quote Originally Posted by GRAHAM WALLIS View Post
    Better check which model it actually is. Does it have chrome tops to the door trims?
    I THINK this is what you are asking? If so, yes?
    Attached Images Attached Images

  9. #9
    VIP Sponsor
    Join Date
    Aug 2000
    Posts
    9,137

    Default

    No,on the inside. Should have said door cards perhaps.

  10. #10
    Member
    Join Date
    May 2015
    Location
    Adelaide
    Posts
    102

    Default

    Quote Originally Posted by GRAHAM WALLIS View Post
    Could have had discs fitted to a 68, with important bits missing, or even wrong bits on a 1969. If a disc brake master is fitted to a 68 without adding the 1969 4 way junction on the cross member there won't be a line pressure valve for the rears and the pedal feel and level will be bad.Also, locking rears suggests no limiting valve on rear axle, or maybe just seized?
    Reasonably sure the disks are original, I feel like it would have been mentioned in the car's rather complete history.

    It does appear to have the four way junction...
    Attached Images Attached Images

  11. #11
    Member
    Join Date
    May 2015
    Location
    Adelaide
    Posts
    102

    Default

    Quote Originally Posted by GRAHAM WALLIS View Post
    Could have had discs fitted to a 68, with important bits missing, or even wrong bits on a 1969. If a disc brake master is fitted to a 68 without adding the 1969 4 way junction on the cross member there won't be a line pressure valve for the rears and the pedal feel and level will be bad.Also, locking rears suggests no limiting valve on rear axle, or maybe just seized?

    The limiting valve is there, sounds like I am going to have to remove it and see what is going on.

  12. #12
    Member
    Join Date
    May 2015
    Location
    Adelaide
    Posts
    102

    Default

    Quote Originally Posted by robmac View Post
    I'd think with front disks and a booster It also has an anti lock valve.
    What does that look like please, and where would I find it?

  13. #13
    Member
    Join Date
    May 2015
    Location
    Adelaide
    Posts
    102

    Default

    Quote Originally Posted by robmac View Post
    It's not easy -generally all you can do is check the piston moves when pressed. And of course the rear brakes don't lock up prematurely.

    I've not seen one leak.

    Here's a thought with car on it's wheels do you get any change in brake "feel" if you pull on the handbrake ?

    Yes, prior to this event, I realised i had to adjust the rear brake shoes because the brakes were noticeably better with the handbrake partially applied.

    That would indicate the rear brakes are getting fluid to them.

    The only other way is to crack a brake fitting and look for fluid squirting.
    -----

  14. #14
    Member
    Join Date
    May 2015
    Location
    Adelaide
    Posts
    102

    Default

    Quote Originally Posted by GRAHAM WALLIS View Post
    No,on the inside. Should have said door cards perhaps.
    Ummm... not sure now... does this help?
    Attached Images Attached Images

  15. #15
    VIP Sponsor
    Join Date
    Aug 2000
    Posts
    9,137

    Default

    Quote Originally Posted by Gilow View Post
    Reasonably sure the disks are original, I feel like it would have been mentioned in the car's rather complete history.

    It does appear to have the four way junction...
    They both have 4 way junctions but different, this IS the proper disc brake one.

  16. #16
    Member
    Join Date
    May 2015
    Location
    Adelaide
    Posts
    102

    Default

    Quote Originally Posted by robmac View Post
    ...

    The only other way is to crack a brake fitting and look for fluid squirting.
    Oh, yeah, silly me... I just bled the brakes on all four wheels, so fluid is definitely getting through ok.

  17. #17
    1000+ Posts robmac's Avatar
    Join Date
    Nov 2004
    Location
    Melbourne / Caulfield
    Posts
    18,772

    Default

    I'd be taking a good look at the master and the flexible hoses then.

    The hoses can can be economically reproduced by any brake shop with a Brakquip hose making machine.

    The 404 hose ends are a standard off the shelf fitting. Just take the original hoses to the shop.

    You can even have road legal braided hoses in lieu of standard neoprene.

  18. #18
    Member
    Join Date
    May 2015
    Location
    Adelaide
    Posts
    102

    Default

    Quote Originally Posted by robmac View Post
    I'd be taking a good look at the master and the flexible hoses then.

    The hoses can can be economically reproduced by any brake shop with a Brakquip hose making machine.

    The 404 hose ends are a standard off the shelf fitting. Just take the original hoses to the shop.

    You can even have road legal braided hoses in lieu of standard neoprene.

    Will do, but I reckon something else is amiss. The master feels and looks good, and it maintains its position under sustained pressure. The locking problem only appeared after I changed the booster, so I guess it might be the culprit there.

    I am looking at some stuff in the manual about residual pressure valves and wondering if the vh40 booster has one of those, because the description fits some of what I am seeing since the booster changeover.

  19. #19
    Member
    Join Date
    May 2015
    Location
    Adelaide
    Posts
    102

    Default

    One forum (on old holdens) mentions problems with a "minimum pressure valve" in the master cylinder causing problems with the VH40 booster. Could it be there is something like this in the 404 master cylinder?

  20. #20
    VIP Sponsor
    Join Date
    Aug 2000
    Posts
    9,137

    Default

    Quote Originally Posted by Gilow View Post
    One forum (on old holdens) mentions problems with a "minimum pressure valve" in the master cylinder causing problems with the VH40 booster. Could it be there is something like this in the 404 master cylinder?
    This valve will cause problems with disc brakes as it will tend to hold them on. It is only for drums, which is why it is included in the rear output of that 4 way junction mentioned before. It is in the base of the master cylinder for 4 wheel drum braked cars and would be diabolical if fed into a booster, would hold the brakes on slightly.

    Maybe the one in the junction isn't working, causing the poor pedal?

    Also, there is virtually no chance the rear brake limiter valve is still working after all these years, maybe fit an adjustable aftermarket device? Superstop in Mont Albert, Melbourne could reco the original valve using parts from elsewhere, original bits no longer available, try contacting them?

  21. #21
    1000+ Posts robmac's Avatar
    Join Date
    Nov 2004
    Location
    Melbourne / Caulfield
    Posts
    18,772

    Default

    Quote Originally Posted by Gilow View Post
    One forum (on old holdens) mentions problems with a "minimum pressure valve" in the master cylinder causing problems with the VH40 booster. Could it be there is something like this in the 404 master cylinder?
    AFAIK the disk brake 404 master doesn't have a residual pressure valve.

    If the braking system has been working properly at an earlier time then I'd think you are looking at something which has failed due to wear or age.

    The master and/or hoses fit that hunch. Check if booster has fluid in it too.

  22. #22
    VIP Sponsor
    Join Date
    Aug 2000
    Posts
    9,137

    Default

    No, residual pressure valve in disc brake 404 is in the 4 way junction as mentioned above.

  23. #23
    Fellow Frogger! Dijon16's Avatar
    Join Date
    Jan 2005
    Location
    Sydney
    Posts
    363

    Default

    I had a 1970 404 with the problem of the rear drums locking under heavier-than-usual braking, and the back wanting to overtake the front.

    It turned out that the proportioning valve had the lines connected in the wrong position, which I think gave it some kind of bias.

    Can't remember all the details, it was 40 years ago.

  24. #24
    Member
    Join Date
    May 2015
    Location
    Adelaide
    Posts
    102

    Default

    OK, some good ideas so far...

    Looking at things as they stand.

    1. The original VH44 booster gave adequate boost, but I have been suspicious of it for some time, hence I was happy to swap it out.
    2. The swap to the reco VH40 seems to have introduced a lot of problems, perhaps it is no good.
    3. The rear limiting valve probably is kaput, though it was reconditioned or replaced some time in the last 15 years. (yeah, not exactly mint condition.)
    4. Most of the hoses have been replaced already by me, but I will double check that I have not missed anything...

    So, where to from here? Nothing obvious is jumping out to anyone, so I am inclined to just start replacing stuff with new bits, on the basis that this can't be a BAD thing. I will see about adjustable rear limiter vs reco, like the idea of something new if I can.

    Regarding the booster... there is a HUGE price difference between the VH40 and the VH44. Given the VH44 was previously giving enough boost for his kind of driving (he's an extremely conservative driver thanks to his various levels of flight training.), is there any reason NOT to get another VH44 aside from boost levels? The car is used almost exclusively as a daily runabout and would rarely go over 60 km/h.

    If I can source an aftermarket limiter, can anyone point me in the direction of data on the pressure settings for the genuine article?

    Also, I would like to replace the master cylinder completely, aside from the usual European suppliers, can anyone recommend a local (Australian) supplier?

    Matt

  25. #25
    Member
    Join Date
    May 2015
    Location
    Adelaide
    Posts
    102

    Default

    Quote Originally Posted by Dijon16 View Post
    I had a 1970 404 with the problem of the rear drums locking under heavier-than-usual braking, and the back wanting to overtake the front.

    It turned out that the proportioning valve had the lines connected in the wrong position, which I think gave it some kind of bias.

    Can't remember all the details, it was 40 years ago.
    Yes, that would do it, but I am confident that I have not changed the position of any of those lines in this case, so the problem of jamming must be something else.

Page 1 of 3 123 Last

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •